Modified polyamines grafted to a particulate, solid support as sorbent materials for removal of target substances from fluids

ABSTRACT

Provided are compositions for removal of a target substance from a fluid stream, the composition comprising a polyamine; and a covalently linked hydrophobic group, wherein the polyamine is covalently linked to a support material. Also provided are processes for removal of a target substance from a fluid stream comprising contacting the fluid stream with a composition comprising a polyamine; and a covalently linked hydrophobic group, wherein the polyamine is covalently linked to a support material.

FIELD OF THE INVENTION

The invention is concerned with the removal of target substances fromfluids, such as liquids, using chemically modified filtration materialsbased on polyamines, as well as methods for the production of suchmaterials.

BACKGROUND OF THE INVENTION

Growing industrialisation around the world, combined with increasingdemand for cheaply manufactured products, has contributed to asignificant and on-going need for the remediation and recycling ofcontaminated supplies of key solvents, such as water. There is anappreciation that it is necessary to re-use and replenish existingresources rather than simply dispose of them. Environmental protectionregulations have also become increasingly stringent as dwindling freshwater supplies have become threatened with contamination from industrialactivity.

Important fluids used in industrial and agricultural processes includenot only water, but also solvents, fuels, lubricants and working fluids.All of these fluids can be exposed to chemical contamination throughnormal use in industrial processes, or via exposure to waste products,whether intentionally or accidentally. By way of example, inindustrialised countries typically up to two thirds of all waterconsumption can be attributed to the needs of industry. It is notsurprising that at an international level there are significant effortsfrom organisations such as the United Nations to ensure that developedand developing nations commit to sustainable environmental policiesincluding the responsible use of water. In particular, it is essentialthat better ways of getting more out of each unit of water consumed aredeveloped to support sustainable growth.

There are diverse sources of environmentally damaging pollutants,including wastewater from industrial plants and chemical processfacilities which has been improperly disposed of; surface runoffcontaining fertilisers and pesticides used on agricultural areas; andcleaning detergents as well as flame retardants used in fire-fightingfoams. Many industrial chemical contaminants can persist in nature formany years before degrading, and can cause great harm to plants, animalsand humans, even at very low concentrations. The impact on ecologicalsystems is also profound, with persistent pollutants often concentratingin the bodies of organisms higher up the food chain. Despite beingbanned in most industrial nations in the late 1970s, polychlorinatedbiphenyls (PCBs) can still be found at high levels in the tissues ofmany marine animals, causing disruption of normal endocrine processes.

In addition to environmentally damaging pollutants, it is also commonfor fluids used in industrial, pharmaceutical and agricultural processesto contain economically valuable components or chemicals, such asprecious metals including silver or or gold, palladium and platinumgroup metals (Sharma et al 2017https://pubs.rsc.org/en/content/articlehtml/2017/ra/c7ra10153h), othermetals including lithium, or small molecules including drugs. While inmany contexts such chemicals can often be viewed as harmful contaminantsin their own right, removal and/or reclamation of these contents canalso be valuable in that they can then be reused, rather than lost. Forexample, water (such as rainwater) passing through refuse from miningoperations can contain dissolved minerals which were present atconcentrations too low to be worth refining, but which could both posean environmental hazard, and represent a possible source for increasingproduction from mining.

Hence, there exists a significant need to provide novel and innovativesolutions to the problem of remediation of contaminated fluid streams,especially contaminated water.

One particular class of persistent environmental pollutants includeshalogenated organic compounds such as poly- and perfluorinated alkylsubstances (PFAS). PFAS are organofluorine compounds. Whilst they areconsidered to be chemically inert, they are persistent in theenvironment, and their use is controlled in many countries by the UnitedNations Framework Convention on Climate, the “Kyoto Protocol”. PFAS arealso used as precursors for the manufacture of a number of derivativecompounds that do represents an environmental risk, includingfluorosurfactants, fluoropolymers and organofluorine reactants.Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) aretoxic PFAS compounds that are used extensively as surfactants and inflame retardants for fire-fighting foams and metal plating processes.Both PFOS and PFOA persist in the environment for very long periods oftime and are recognised contaminants in most of the world's fresh watersupplies.

Adsorption of PFAS compounds such as PFOS and PFOA, onto granularactivated carbon represents the current best and recommended solutionfor their removal from contaminated water. However, the process is veryslow and inefficient. In particular, the charged and shorter chain, PFASpollutants quickly “break-through” beds of activated carbon, meaningvery large quantities of activated carbon are required, which must befrequently replaced once saturated with PFAS. Adsorbed PFAS cannot bewashed off activated carbon for regeneration “in situ”. Hence, theactivated carbon represents an expensive and single use solution to theproblem of removing PFAS from contaminated water.

Some modified cellulose materials show better removal, but have onlybeen effective at reducing high concentration perfluorinated surfactantsto lower levels, not at cleaning them completely from levels at >1 ppmto within regulatory limits (for example set by the United StatesEnvironmental Protection Agency around 70 parts per trillion:https://www.epa.gov/ground-water-and-drinking-water/drinking-water-health-advisories-pfoa-and-pfos).Such materials have only been effective as a pre-treatment to extend thelife of activated carbon, not as a complete solution to PFC removal.They also act as a dispersed flocculant and require complex and uniqueequipment for implementation (see for example, EP2763790B1).

Speciality ion exchange resins are also an emerging solution. Here,styrene divinyl benzene polymer beads, modified with quaternaryammonium, are used in packed beds as an alternative to activated carbon.These resins either cannot be regenerated or can only be regeneratedwith a toxic and flammable solvent (see for example WO2017180346A1).

Hence, there exists a need to provide economical and re-usablecompositions and processes that enable the removal of low concentrations(<1 ppm) of target substances, in particular valuable materials, orpolluting contaminants, such as PFAS, from fluid streams, such aswastewater. It is apparent that such a goal is especially challengingwith current technologies. The present invention seeks to overcome thepresent challenges and meet these objectives.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a composition for removal of atarget substance from a fluid stream, the composition comprising apolyamine; and a covalently linked hydrophobic group, wherein thepolyamine is covalently linked to a support material.

The support material may typically be a porous, solid and/or particulatesupport material. Suitably the support material comprises cellulose, andis comprised of a material selected from one or more of the groupconsisting of: lignocellulose; microcrystalline cellulose;microfibrillated cellulose; bacterial cellulose; and a cellulosederivative. Optionally, the support material can be a powder or pulp,such as a cellulose or lignocellulose powder or pulp. If in particulateform, the support material can comprise for example one or more of thegroup consisting of a plurality of: granules; flakes; beads; pellets;and pastilles.

The support material may also be selected from one or more of the groupconsisting of: silica; silica gel; and a silica derivative.

In an embodiment of the invention, the polyamine is selected from alinear or branched polyamine. Suitably the polyamine is selected from alinear or branched polyamine selected from: polyethylenimine (PEI);polypropylenimine (PPI); poly(allylamine), poly(vinylamine),poly(N-methylvinylamine)polylysine, poly(4-aminostyrene).

In an alternative embodiment of the invention, the polyamine is selectedfrom a cationic polyamine such as poly(diallyldimethylammoniumchloride), a guanidine polyamine such as polyhexamethylene guanidine orpolyhexanide, or a polyamine copolymer such aspoly(acrylamide-co-diallyldimethylammonium chloride) or poly(methyleneco-guanidine).

In a further embodiment the hydrophobic group comprises a group selectedfrom: a C2-C22 branched, linear or cyclic, saturated or unsaturatedalkyl; or an aryl. Typically, this group is selected from a C2-C22branched, linear or cyclic alkyl; or an aryl. Optionally the C2-C22branched or linear alkyl group is selected from a butyl, hexyl or octylgroup. Suitably, the C2-C22 linear alkyl group is a C4-C8 branched orlinear alkyl selected from an isobutyl, isohexyl or isooctyl group. In aspecific embodiment of the invention the C2-C22 alkyl group is acycloalkyl selected from a cyclohexyl, cycloheptyl or cyclooctyl group.In a further embodiment, the aryl group is selected from the groupconsisting of: a phenol, benzene or benzyl. In a further embodiment thehydrophobic group is a C2-C22 poly or perfluorinated group, suitably aC8 perfluorooctane or C8 polyfluorinated, 6:2 fluorotelomer. Optionallythe sorbent molecule comprises a plurality of hydrophobic groups.

According to specific embodiments of the present invention, thepolyamine group is linked to the hydrophobic group via an amide bond.The polyamine and hydrophobic group may alternatively be linked via aurea linkage, a thiourea linkage; an isothiouronium linkage, aguanidinium linkage or directly via an alkylation reaction, or aquaternisation (Menshutkin) reaction.

A second aspect of the invention provides for a process for removal of atarget substance from a fluid stream comprising contacting the fluidstream with a composition comprising a polyamine; and a covalentlylinked hydrophobic group, wherein the polyamine is covalently linked toa support material.

Typically the fluid is a liquid, optionally the liquid is selected from:water; an organic solvent; a liquid fossil fuel; a liquid lubricant; anda working fluid.

In a specific embodiment of the invention, the target substance is acontaminant. The contaminant may comprise one or more poly- andperfluorinated alkyl substance (PFAS), optionally selected from aperfluorinated anionic surfactant compound, including one or moreselected from the group consisting of: perfluorooctanoic acid (PFOA);perfluorobutane sulfonate (PFBS); perfluorobutanoic acid (PFBA);perfluorohexanesulfonate (PFHS); perfluorohexanoic acid (PFHA);perfluorooctane sulfonate (PFOS); perfluorononanoic acid (PFNA); andperfluorodecanoic acid (PFDA). Alternatively, the contaminant maycomprise an organic compound, optionally a pharmaceutical or pesticidemolecule including one or more selected from the group: diclofenac,erythromycin, estrogens, oxadiazon and thiamethoxam.

Alternatively the contaminant may be a metal or metalloid ion optionallyselected from copper, iron, lead, mercury, chromate or arsenate.

In another embodiment of the invention, the target substance comprises avaluable substance. optionally comprising gold, silver, rare earthmetals or platinum group metals or their salts.

In a specific embodiment the support material is deployed within a bedor a packed column and the fluid stream is passed through or across thebed or packed column.

According to a further embodiment of the invention the process furthercomprises regenerating the composition after removal of the targetsubstance from the fluid stream. Suitably, the step of regenerating thecomposition comprises applying an aqueous wash to the sorbent materialor a series of washes. Optionally, regeneration of the support materialcomprises applying a salt wash, or acidic wash or basic wash to thecomposition. The wash may comprise a liquid having a pH greater than 9,or alternatively a pH of less than 5. In some embodiments, regenerationof the support material comprises applying an aqueous ammoniumhydroxide, aqueous ammonium chloride or ammonium sulphate wash to thecomposition, either in addition to or instead of other salt, base oracid washes.

A third aspect of the invention provides a method for manufacturing acomposition for removal of a target substance from a fluid stream, themethod comprising:

providing a support material;linking this support material covalently to a target-substance-sorbentmolecule that comprises:

-   -   a. a polyamine group; and    -   b. a covalently linked hydrophobic group.

It will be appreciated that the above statements are to be read inconjunction with the embodiments described in further detail below. Eachembodiment of the invention may be utilised in isolation or incombination with other embodiments, unless otherwise specified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an electron micrograph of a composition according to anembodiment of the invention.

FIG. 2 shows graphs comparing adsorption kinetics of PFAS compoundsbetween a composition according to the invention (CGM), and bituminousgranular activated carbon (GAC).

FIG. 3 demonstrates improved binding capacity for PFAS compounds insimulated wastewater with competing organic acids shown by a compositionaccording to the invention (CGM), compared to a bituminous granularactivated carbon (GAC) and an amberlite anion exchange resin.

FIG. 4 shows performance of a composition according to the invention atadsorbing PFOA and PFHS from batch tests at a range of pH values.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise indicated, the practice of the present inventionemploys conventional techniques of chemistry, materials science andprocess engineering, which are within the capabilities of a person ofordinary skill in the art.

Prior to setting forth the invention, a number of definitions areprovided that will assist in the understanding of the invention. Allreferences cited herein are incorporated by reference in their entirety.Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

As used herein, the term ‘comprising’ means any of the recited elementsare necessarily included and other elements may optionally be includedas well. ‘Consisting essentially of’ means any recited elements arenecessarily included, elements that would materially affect the basicand novel characteristics of the listed elements are excluded, and otherelements may optionally be included. ‘Consisting of’ means that allelements other than those listed are excluded. Embodiments defined byeach of these terms are within the scope of this invention.

The term ‘target’ or ‘target substance’ refers herein to a substance orcompound which it is desired to remove or isolate from a fluid. Targetsubstances can be dissolved (i.e. a solute), suspended, emulsified,dispersed, or otherwise carried in the fluid, and as such may besoluble, partially soluble or insoluble in the fluid. As discussedbelow, target substances can comprise contaminant substances and/orvaluable substances which it is desired to remove, and in some casesrecover, from the target fluid.

Target substances as contemplated herein can include ‘contaminants’ or‘contaminant substances’. In the context of the present invention,‘contaminants’ are intended to encompass substances which may be harmfulto the health of humans or animals, or to the environment. Consequently,derivative terms are defined accordingly, for example, a contaminatedfluid is a fluid comprising a contaminant substance. Typically, thecontaminant comprises one or more per- and polyfluoroalkyl substances(PFAS), typically one or more perfluorocarbons, optionally selected froma perfluorinated anionic surfactant compound, including one or moreselected from the group consisting of: perfluorooctanoic acid (PFOA);perfluorobutane sulfonate (PFBS); perfluorohexanesulfonate (PFHS);perfluorohexanoic acid (PFHA); perfluorooctane sulfonate (PFOS);perfluorononanoic acid (PFNA); and perfluorodecanoic acid (PFDA) 6:2fluorotelomer sulfonic acid (6:2 FTSA). In some embodiments, thecontaminant comprises an organic compound, optionally a pharmaceuticalor pesticide molecule including one or more selected from the groupconsisting of: diclofenac, erythromycin, estrogens, oxadiazon andthiamethoxam. The contaminant may in some embodiments be a metal ormetalloid ion, optionally selected from copper, iron, lead, mercury,chromate or arsenate.

The target substance may be a valuable substance. A substance may bevaluable if it contains rare elements or molecules, is a complexmolecule which is difficult to manufacture, or is in any other wayeconomically valuable enough to want to recover from a fluid. Valuablesubstances may be present in a fluid as a result of manufacturing,refining, mining, purification, or recovery processes. In some cases,valuable substances may also in their own right be contaminants, forexample if they are harmful to the health of humans or animals, or tothe environment. Valuable substances may suitably be precious metals,rare earth metals, base metals, or platinum group metals, or saltsthereof. Precious metals may include gold and silver. Platinum groupmetals may particularly include platinum and palladium. Valuablesubstances may in some embodiments be small molecules, such as drugs orfine chemicals.

The term ‘fluid stream’ or ‘fluid’ refers to a flowable substance inwhich the target substance is dissolved, suspended, emulsified,dispersed, or otherwise carried. The fluid can be for example a liquid,or a gas. Suitably the fluid is a liquid, optionally the liquid isselected from: water; an organic solvent; a liquid fossil fuel; a liquidlubricant; an ionic liquid; a working fluid; and mixtures thereof.

The term ‘cellulose’ refers to a biological polymer which is a linearpolysaccharide composed of glucose monomers linked with β(1→4)glycosidic bonds. Cellulose may also refer to material which furthercomprises hemicellulose, a polysaccharide composed of glucose and othermonosaccharides, which is branched and has shorter chains than are foundin cellulose.

Lignocellulose, or lignocellulosic biomass, refers to a biologicalmaterial comprising cellulose and lignin, which may also comprisehemicellulose and pectin. Lignocellulose comprises much of the biomassof plants and as such is known for its high availability and resistanceto degradation. This resistance is a consequence of the lignin moleculescreating crosslinks between cellulose and hemicellulose chains throughester and ether linkages, Lignocellulose may be obtained from a numberof sources, which include any terrestrial plant matter harvested for thepurpose, or industry-related feedstocks or waste biomass produced fromsources such as agriculture, forestry, construction, pulp and paperproduction and biofuel production. Typically, lignocellulose is obtainedfrom agricultural wastes such as pips, husks, shells and stover(discarded leaves and stalks after the harvesting of grain). Inparticular, the lignocellulose can be derived from nut shells or thepips, stones, seeds or pits of fruits. The lignocellulose is dried, thencrushed and sieved to the predetermined particle size.

The terms ‘bacterial cellulose’, ‘microbial cellulose’, ‘nanocellulose’,‘bacterially produced cellulose’ and ‘bacterially producednanocellulose’ as used herein are equivalent and refer to celluloseproduced by bacteria or microorganisms, such as species from the generaof Gluconacetobacter, and others, that is characterised by high tensilestrength, high tensile stiffness, high chemical purity, biocompatibilityand high water-to-cellulose ratio. Suitably such bacterial nanocellulosewill be substantially free of associated molecules typically present inplant-derived cellulose such as lignin. Microfibrillated cellulose'refers to cellulose processed by mechanical treatment with or withoutenzymatic or chemical pre-treatment. The material consists of long thinfibres, micrometers in length. Microcrystalline cellulose' refers to apure partially depolymerized cellulose produced by breaking downamorphorous regions of the cellulose via physical, chemical or enzymaticmeans to leave crystalline domains.

The term ‘modified’ as used herein in the terms ‘modified cellulose’ or‘modified lignocellulose’ refers to cellulose or lignocellulose whichhas been modified by the addition of chemical compounds. These compoundsmay be linked to the cellulose or lignocellulose by covalent bonds,ionic bonds, electrostatic bonds or affinity interactions. Modificationmay include where a chemical compound linked to the cellulose orlignocellulose is subsequently itself modified by reaction with anothercompound, and so forth. In particular, it is envisaged that cellulosemay be modified by the addition of target substance sorbent molecules.Other possibilities for modification include the addition of polyaminegroups, typically polyethylenimine. The polyamine groups may be linearor branched and are suitably branched polyethylenimine. The polyaminegroups may themselves be further modified by the addition of furtherchemical groups, such as hydrocarbon groups.

The term ‘silica’ refers to materials comprising of silicon dioxide,with the formula SiO2. These may or may not be hydrated and may in agranular, porous form referred to as ‘silica gel’. Alternatively, thesilica-based material may be a silicate mineral such as sodium silicate.

The term ‘sorbent material’ as defined herein refers to a materialcomprising a support material, which further comprises a sorbentfunctional group. The sorbent material is suitable for contacting afluid stream that comprises a target substance, such as a contaminant,which may be a PFAS, such that the target substance is adsorbed onto,absorbed into, or otherwise taken up by the sorbent material. Suitablythe sorbent material is deployed within a bed or a packed column and thefluid stream is passed through or across the bed or packed-column. Thesorbent material may be deployed within a mixed bed combined withanother adsorbent material such as granular activated carbon or anion-exchange resin. In one embodiment the sorbent material is comprisedwithin a prepared component such as a cartridge, so that used sorbentmaterial can be conveniently contained, and similarly replaced orreplenished with fresh or regenerated sorbent material as necessary.Alternatively, the sorbent material may be added to the fluid as adispersion. The sorbent material may be particulate, that is to say inthe form of granules; flakes; beads; pellets; or pastilles. The sorbentmaterial may be a powder or a pulp, in particular a cellulose,microfibrillated cellulose, microcrystalline cellulose, orlignocellulose powder or pulp which can advantageously provide higheraccessible surface area. The sorbent material may be incorporated into amembrane, or membrane-like filter. In particular, a pulp can be used tomake membranes or membrane-like products, which can be used to makefilters. An advantage of filters of this kind is that they can be madewith specific thickness, and with a large surface area, while alsoensuring that fluid passes through when appropriately installed in afluid flow path. Typically, the sorbent material is particulate orgranular in form, suitably the average diameter size of the particles orgranules (as measured by the largest diameter of the particles) isgreater than about 0.01mm, suitably greater than about 0.1 mm, andtypically less than about 1 mm, and optionally less than 10 about 500μm.

The term ‘sorption’, ‘sorb’, ‘sorbent’ and derivatives as used hereinrefer to the removal of target substances such as contaminants from thefluid stream by the association of said target substances with themodified support material described. Sorption by the material may happenby any means, for example by adsorption to the surface of the material,which may be by the creation of chemical bonds between the targetsubstance and the support material, including electrostatic attraction,the formation of covalent bonds, ligation, chelation, van der Waalsforces, hydrogen bonds, or otherwise. ‘Sorption’ also refers toabsorption of the target substance into the material. The targetsubstance may become physically trapped inside intermolecular space,pores or other voids within the material. In particular, sorption may beadsorption occurring by the formation of chemical interactions betweenthe target substance molecule and the sorbent molecule with which thesorbent material has been modified. Such chemical interactions lead tothe sequestration of the target substance within the sorbent materialand out of the fluid stream. Use herein of the term ‘adsorption’ orderivatives thereof is not intended to be bound by any theoreticallimitation, but rather is intended to include sorption by other means,as defined above, except where otherwise specified.

In one embodiment of the present invention there is provided acomposition for removal of target substances and/or contaminants from afluid stream. The composition comprises a sorbent material comprising asupport material covalently linked to a target substance sorbentmolecule. The support materials have high surface area to volume ratioand therefore provide an efficient support for molecules which are ableto act as sorbents for target substances. The granular sorbent particlesare designed to be deployed as a sorbent media for wastewater treatmentin a standard packed bed. The granules have some porosity but are hard,durable and resistant to degradation.

Where the sorbent material comprises cellulose, the particles may beproduced from agricultural waste such as stover, pips and shells, andprocessed into granular particles by crushing and sieving. Afterchemical modification with target substance sorbent molecules asdiscussed below, the sorbent granules can be deployed in a standardpacked filtration bed or column, as with other media deployed in thisway (granular activated carbon or ion-exchange resins). They may bepositioned such that they are contacted by a fluid stream such aswastewater comprising target substances. The fluid stream may flow overor through the granules by positive or negative pressure, such asimplemented by a gravity feed, or pumping, vacuuming or otherwiseimpelling the fluid stream by any suitable means. Sorption occurs of thetarget substances by the granular sorbent material and the targetsubstances therefore remain in situ whilst the water flows through andhas the target substance removed. The filtration bed or column may beoccasionally backflushed, to clear build-up of occlusions, such asorganic matter or lime scale, that reduce flow rate.

According to an aspect of the invention, the sorbent molecule comprisesa polyamine group. Polyamines are compounds comprising more than twoamino groups. Typically, the sorbent molecules comprise polymers basedon polyamines typically in the molecular weight range of 500 to 50,000Daltons (Da). For example, the minimum average molecular weight of thepolymers may typically be at least 500, at least 1000, at least 2000, atleast 3000, at least 5000, suitably at least 10,000 Da. The maximumaverage molecular weight of the polymers may suitably be at most 50,000,at most 45,000, at most 40,000, at most 35,000, typically at most 30,000Da. These polymers may be linear or branched. Highly branched polyaminepolymers, typically termed ‘dendrimers’, comprise a plurality of primaryamino groups on each polymer molecule. It is advantageous, in certainembodiments, if the polyamines utilised in the sorbent molecules of theinvention comprise at least one terminal amine, typically thedendrimeric polyamines will comprise a plurality of terminal amines.Suitably, the sorbent molecule comprises polyethylenimine ‘PEI’ (alsoknown as polyaziridine) which is a polymer composed of multiple aminegroups, each linked with a saturated two carbon spacer. Typically thepolyethylenimine molecules are branched, that is, they contain tertiaryamine groups at branch points and primary amine groups at the terminusof each branch. Branched polyamines have lower melting points and highersolubilities, which offer advantages in production processes. In thesorbent compositions they may have steric advantages with the aminesspatially arranged to allow cooperative interactions with the targetmolecules. In further embodiments the polyamine may comprises a linearor branched polypropyleneimine (PPI). In yet further embodiments of theinvention the polyamine may comprises a linear polyamine such as, butnot limited to, poly(allylamine), poly(vinylamine),poly(N-methylvinylamine)polylysine, and poly(4-aminostyrene). In analternative embodiment of the invention, the polyamine is selected froma cationic polyamine such as Poly(diallyldimethylammonium chloride), aguanidine polyamine such as polyhexamethylene guanidine or polyhexanide,or a polyamine copolymer such aspoly(acrylamide-co-diallyldimethylammonium chloride).

Polyamines and modified polyamines on solid supports have previouslybeen used as sorbent materials for gases, particularly carbon dioxide(see for example WO2015084521A1). In water treatment, polyamines boundto solid support materials have been shown to be effective at removingheavy metals and dyes (see for example CN103041780B). However, theireffectiveness at removing anionic surfactants from water is surprising.In particular, sorbent granules modified with flexible branchedpolyamines according to an embodiment of the invention can remove PFASfrom wastewater down to regulatory limits with faster, more efficientsorption than activated carbon and lower cost than specialityion-exchange resins. In addition, unlike with activated carbon andresins, the sorbent material can then be regenerated with an aqueousliquid wash, to recover the pollutants and reuse the sorbent material.Flexible, branched polyamines allow stronger, more specific interactionswith these target pollutants. In addition, branched polyamines providemultiple amine groups where subsequent chemical substitution ispossible, allowing a high degree of substitution, without the necessityfor a high level of chemical modification of the cellulose itself. Thistends to increase the capacity for sorption of target substances.

Before the addition of target substance sorbent molecules, it may benecessary or desired to activate the support substrate. This activationcomprises the addition of a functional group to the cellulose or silicasurface. In subsequent reactions, the target substance-sorbent moleculethen forms a bond with the functional group added during activation, andso is linked to the support material. The covalent linkage may be via anester, an ether, a carbamate, or a thiocarbamate linkage. In someembodiments, a cellulose support is activated by reaction withhalogenated acyl halides, typically bromoacetyl bromide. Chemicallyrelated groups with different chain lengths (methyl, propyl, butyl,pentyl, and so on) are also considered for use in this activation. Inother embodiments the cellulose is activated by reaction withcarbonyldiimidazole, or a cross-linking agent such as glutaraldehyde orepichlorohydrin. These activating functional groups provide chemicalattachment points for the target substance-binding molecules with whichthe cellulose is eventually modified. These attachment points can resultin a short linker existing between the support and the targetsubstance-binding molecules. This linker may be, for example, that leftby acylation with the halogenated acyl halides mentioned above(—C(═O)—C—).

In another embodiment, a granular, porous, silica gel substrate isactivated by reaction with (3-Chloropropyl)trichlorosilane. Thisprovides the chemical attachment point for formation of a covalent bondto the selected polyamine in a subsequent step.

According to the invention, the sorbent molecule comprises a polyaminegroup that is itself modified by the addition of a further chemicalgroup that is suitably a short chain hydrophobic group. Typically thisfurther chemical group is added by reaction of an alkyl or aryl acidhalide or anhydride with an amine group of the polyamine group to forman amide bond between the polyamine and the hydrophobic group.Optionally the reaction is between the hydrophobic group and a terminalprimary amine group comprised within the polyamine molecule. Inembodiments of the invention, a plurality of hydrophobic groups arereacted with a plurality of amine groups within the polyamine molecule.In some embodiments, substantially all the terminal primary amine groupspresent within the polyamine molecules are reacted with a hydrophobicgroup.

The resultant sorbent molecule will possess unique properties ofsorbency that may be tuned to the specific requirements of the sorbentmaterial. Hence, it is an advantage of the present invention that thesorbent material may be readily optimised to target specific substancesand/or contaminants within a fluid stream by modifying the chemistry ofthe sorbent molecule.

The primary targets for treatment in wastewater are poly orperfluorinated surfactants such as PFOA, PFOS, PFHA, PFHS, PFBA, PFBSand 6:2 FTSA.

It is also envisioned that treatment of wastewater to remove othertarget substances, contaminants or valuable substances (includingprecious or rare earth metals, for example present in wastewater frommining, purification or manufacturing processes), or treatment of otherfluids such as organic solvents and oils or removal of impurities fromliquid product streams, is possible. In addition, sorbent materialaccording to the present invention could be used as a sorbent to removetarget substances from gases.

Unlike other sorbents deployed in this way for organic pollutants, thegranular sorbent material can be effectively regenerated in situ with anaqueous liquid wash. The liquid wash can comprise a salt wash, an acidwash, a basic wash, or a combination, such as a salt and acid wash.Suitably, the wash can comprise a liquid having a pH greater than 9, oralternatively a pH of less than 5. Optionally the wash solutioncomprises an aqueous ammonium hydroxide, ammonium chloride or ammoniumsulphate solution. The possibility of regeneration is particularlyadvantageous, in that it allows for the removal of target substances forrecycling, recovery or safe disposal, as well as allowing the reuse ofthe sorbent material. In this way the proposed method for removingtarget substances is further reduced in cost, and in production of wastein the form of spent sorbent material.

The regeneration process suitably includes removing the sorbent materialfrom the fluid stream and contacting it with an aqueous solution of anacid, base and/or a salt. The acid is suitably selected from aninorganic acid including hydrochloric acid, sulphuric acid, nitric acid,phosphoric acid or alternatively an organic acid suitably selected fromethanedioic acid, hexanoic acid, ethanedioic acid or citric acid. Thesalt is suitably selected from a sodium, potassium or magnesium saltwith a chloride, sulphate or phosphate counter ion. In some embodiments,the wash liquid has a pH less than 5, suitably less than 4, less than 3,or less than 2.

Suitably, the regeneration process can instead comprise contacting thesorbent material with a basic solution, typically aqueous ammoniumhydroxide. Other suitable alkali solutions may be selected from sodiumor potassium hydroxides. In some embodiments, the wash liquid has a pHgreater than 8, suitably greater than 9, or greater than 10.

Without wishing to be bound by theory, the adsorption of targetsubstances to compositions as described herein appears to be the result,primarily, of electrostatic interactions with the polyamine combinedwith hydrophobic-hydrophobic interactions with the covalently linkedhydrophobic group. In the regenerating aqueous wash solution,interactions with anions in the wash such as chloride, sulphate orhydroxide substitute for the electrostatic interactions with anionictarget substances, releasing the target substances in the wash. Raisingor lowering the pH changes the protonation of the polyamine, which mayfurther reduce the electrostatic binding interactions with the adsorbedtarget compounds. The presence of other ions such as ammonium, canimprove the solubility of adsorbed target compounds, further increasingtheir removal in the regenerating aqueous wash.

Another salient advantage of the present system is its low cost and easeof production. Production of granules or other forms of sorbent materialsuch as a pulp, with a relatively low-cost polyamine (PEI) and verylow-cost support material (lignocellulose) allows cost effectiveproduction of the material at large scale (˜1000 kg per batch) allowingdeployment in large volume wastewater applications (megalitres/day flowrate). In addition, the reactions involved with linking the cellulosesubstrate with the target substance-sorbent molecules may be carried outin large scale and, economically, at room temperature and atmosphericpressure.

According to a specific embodiment of the present invention, there isprovided a process for the preparation of a lignocellulose ester that isthen modified with amphipathic groups in order to generate a derivativeproduct with particular utility in filtration and removal of PFAS fromliquid streams. A particular advantage of the product of this embodimentof the present invention is that the process does not require elevatedtemperatures as it can take place at room temperature, nor does thereaction require expensive catalysts, especially metal containingcatalysts. Hence, the process for preparation of the product isrelatively energy efficient and less resource intensive, thereby addingto the improved economics of production. Further, the process showsadditional advantage in that the resultant product can be regeneratedafter use, reducing the overall consumption of the product and enhancingthe effective working life beyond that of comparable sorbents, as wellas allowing for the recovery of any valuable substances removed from thetreated fluid stream.

In an embodiment of the present invention the lignocellulose/cellulosesupport material is activated by esterification with bromoacetyl bromideat room temperature in the presence of dimethyl formamide (DMF)according to the following reaction scheme I:

-   -   It will be appreciated that in alternative embodiments a        different reactant may be used to esterify the cellulose in a        similar reaction, such as other halogenated acyl halides,        suitably chloroacetyl chloride, chloroacetyl bromide, and        bromoacetyl chloride; or halogen propionyl or butyryl halide.

The bromoacetylated form of the lignocellulose is further reacted with apolyamine also in the presence of DMF at room temperature in order toachieve a highly substituted lignocellulose derivative. In the presentembodiment of the invention, the amine utilised in the second step ofthe reaction is a branched polyethyleneimine (PEI) according to thefollowing reaction scheme II:

It will be appreciated that straight chain (linear) PEI may also beused, as well as other polyamines, such as polypropyleneimine (PPI),poly(allylamine), poly(vinylamine), poly(N-methylvinylamine),polylysine, poly(4-aminostyrene), poly(diallyldimethylammoniumchloride), polyhexamethylene guanidine, polyhexanide, poly(methyleneco-guanidine), or poly(acrylamide-co-diallyldimethylammonium chloride).

In another embodiment the particulate, support material is a silica gel.In this embodiment, the silica surface is hydrated then activated byreaction with Trichloro(3-chloropropyl)silane in hexane solvent. Theproduct is dried, and then the polyamine is covalently bound, byreacting in a methanol solvent according to the following reactionscheme III.

The substituted, particulate solid support product is further reacted ina third step with, for example, an acylating agent, suitably an acyl oraryl acid halide. In the present embodiment of the invention, hexanoylchoride is used in the acyl substitution of primary amines within thePEI group bonded to the solid support. The hexanoyl chloride isdissolved in dichoromethane (DCM) and the reaction is carried out alsoat room temperature in the presence of the base and catalystdiisopropylethylamine (DIPEA), as set out in the following reactionscheme IV, the hydrophobic group is linked to the polyamine via an amidebond:

It will be appreciated that in alternative embodiments of the inventionthe acylating agent may comprise a compound of the formula:

Wherein:

-   -   R₁ is a C2-C22 branched, linear or cyclic alkyl; or an aryl        group    -   R₂ is a halide.

Typically R₁ is selected from a C2-C22, suitably a C4-C8, linearsaturated or unsaturated alkyl 30 group, most suitably selected from abutyl, hexyl or octyl group. Optionally R₁ is selected from anisopropyl, isobutyl or isohexyl group. R₁ may comprise a cycloalkylselected from a cyclobutyl or cyclohexyl group. Where R₁ is an aryl,typically the aryl is selected from a phenol or benzyl group.

R₂ is typically selected from a chloride or a bromide.

Alternatively the polyamine covalently bound to a granular solid supportmaterial may be modified by covalent addition of a C2-C22 hydrophobicgroup by one of the following reactions:

A reaction according to scheme V where the polyamine group is linked tothe hydrophobic group via an urea bond, wherein R₂R₃NH represents thepolyamine group and R₁=C2 to C22. The reaction is performed under basicconditions in an aprotic solvent system.

The urea unit can alternatively be formed by a reaction shown in SchemeVI, wherein R₃R₄NH represents the polyamine group and R₁=C2 to C22 andR₂=H. The reaction is performed under basic conditions in an aproticsolvent system, employing a carbonyldiimidazole derivative.

The urea unit can alternatively be formed by a reaction shown in SchemeVII, wherein R₂R₃NH represents the polyamine group and R₄=C2 to C22 andR₅=H, and R₂=a hydrocarbon unit. The reaction is performed under basicconditions in an aprotic solvent system.

The urea unit can be formed by a reaction shown in Scheme VIII, whereinR₂R₃NH represents the polyamine group and R₁=C2 to C22. The reaction isperformed under basic conditions in an aprotic solvent system and anazide-containing reagent for step 1.

Alternatively, the C2-C22 hydrophobic group may be covalently attachedto the polyamine via a quaternisation (Menshutkin) reaction, resultingin nitrogens of the polyamine becoming bound to up to three C2-C22hydrophobic groups. This may be by a reaction shown in Scheme IX,wherein X=halide, R₄=C2 to C22 hydrophobic group, R₁=part of thepolyamine molecule and R₂ and R₃=R₄ or are part of the polyaminemolecule represented by R₁R₂R₃N.

The invention is further illustrated by the following non-limitingexamples:

EXAMPLE 1

The novel custom granular media (CGM) compositions of the inventiondemonstrate significantly improved capacity for adsorption of PFAS inpart due to their unique structure (see FIG. 1). This Figure shows anelectron micrograph of a composition, comprising porous, solid,particulate, lignocellulose material covalently linked topolyetheleneimine (average mw, 25,000), covalently linked to a pluralityof C6 hydrophobic groups via reaction with hexanoyl chloride. Thecomposition displays surface roughness on a micrometre scale, allowingfor the adsorption of larger quantities of PFAS.

The absorption kinetics of a CGM composition of the invention werecompared with a conventional bituminous granular activated carbon (GAC)media. In the assay 0.05 g of each adsorbent (1 mm average diametergranules) were soaked in 40 mL of 50 ppb PFOA or PFHS in DI water. Atcertain time points aliquots of the solution were taken and PFASconcentrations quantified using Liquid Chromatography-MassSpectrometry/Mass Spectrometry (LC-MS/MS). The results are shown in FIG.2. It can be seen that CGM has much faster kinetics compared to GAC forboth PFOA and PFHS adsorption. In practice, the far superior kineticsseen for CGM translates to significantly reduced contact time fortreatment allowing faster fluid flow rates or use of smaller vessels.Furthermore, the improved kinetics allow for flexible hydraulic loadingrequirements to fit with any required pre- or post-treatment.

EXAMPLE 2

The binding capacity for PFAS of the CGM composition of the inventionwas tested in a simulated waste water comparison to GAC and anAmberlite® anion exchange resin. Batch tests were performed in which0.05 g of adsorbent granules were soaked in 40 mL of 2.5 ppm PFOS, PFOA,PFBS and PFBA in DI water containing 250 ppm competing organic acids.After 24 hours, the PFAS concentration in each of the solutions wasquantified using LC-MS/MS as in Example 1. The results of the tests areset out in FIG. 3. In all instances CGM, the composition of theinvention, outperformed the conventional sorbent media.

EXAMPLE 3

The CGM composition of the invention was tested for adsorptionperformance across a pH range from acidic to basic conditions, as mightbe encountered in waste effluent from industrial or agriculturalsources. According to this assay 0.05 g of adsorbent granules weresoaked in 40 mL of 2.5 ppm, PFOA or PFHS solution in DI water, pHadjusted with NaOH or HCl accordingly. After 24 hours, the PFASconcentration in the solutions was quantified using LC-MS/MS as perExample 1. The results are shown in FIG. 4. As can be seen, high levels(>97%) of PFAS adsorption are observed and remain surprisingly stableacross all of the pH ranges tested.

EXAMPLE 4

The CGM composition of the invention was tested in a rapid small-scalecolumn test for removal of the contaminant PFHS. The contaminated waterinfluent (feed) contained PFHS at 500 ppb and was pumped through smallpacked beds of the CGM composition and a competitor granular activatedcarbon (GAC). The contact time was 22 seconds, with 7.5 m/h linearvelocity. Samples of the effluent solution were taken and PFHSquantified by LC-MS/MS. Results are shown in FIG. 5. The CGM compositionshowed removal of the target contaminant to non-detectable levels over20,000 bed volumes (BV) of influent solution being treated. This was notachieved by GAC, where the conventional sorbent media showed an effluentconcentration which quickly rose to approximately 50 ppb.

EXAMPLE 5

The CGM composition of the invention was mixed with a contaminatedsolution containing PFOA, PFBA and PFBS in a batch test. The CGMcomposition adsorbed 50 μg of total contaminant substance per gram ofmaterial (50 μg/g loading). The loaded CGM media was then packed into an8 ml packed bed. A regeneration solution of 3% aqueous ammoniumhydroxide was pumped through, with a contact time of 15 minutes. Thetotal regeneration solution passed through the column was collected andsampled after every 2 bed volumes (8 ml). PFOA, PFBA and PFBSconcentrations were quantified by LC-MS/MS and total recovery of thecompounds was calculated based on the initial loading amount. Resultsare shown in FIG. 6. The shorter chain PFBA and PFBS are quicklyrecovered and after 6 bed volumes of regenerant solution, all of thetarget substances have been recovered from the sorbent composition, andare present in the spent regenerant solution.

1. A composition for removal of a target substance from a fluid stream,the composition comprising a polyamine; and a covalently linkedhydrophobic group, wherein the polyamine is covalently linked to asupport material.
 2. The composition of claim 1, wherein the supportmaterial is comprised of a material selected from one or more of thegroup consisting of: lignocellulose; bacterial cellulose;microcrystalline cellulose; microfibrillated cellulose and a cellulosederivative.
 3. The composition of claim 2, wherein the support materialcomprises a cellulose or lignocellulose powder or pulp.
 4. Thecomposition of claim 3, wherein the cellulose or lignocellulose powderor pulp is incorporated into a membrane or membrane-like filter.
 5. Thecomposition of claim 1, wherein the support material is selected fromone or more of the group consisting of: silica; silica gel; and a silicaderivative.
 6. The composition of any one of claim 1, 2 or 5, whereinthe support material is porous, solid, and particulate, preferablywherein the average diameter size of the particles is greater than about0.01 mm, and less than about 1 mm.
 7. The composition of claim 6,wherein the particulate form comprises one or more of the groupconsisting of a plurality of: granules; flakes; beads; pellets; andpastilles.
 8. The composition of any one of claims 1 to 7, wherein thepolyamine is selected from a linear or branched polyamine.
 9. Thecomposition of claim 8, wherein the polyamine is selected from a linearor branched polyamine selected from the group consisting of:polyethylenimine (PEI); polypropylenimine (PPI); poly(allylamine);poly(vinylamine); poly(N-methylvinylamine); polylysine;poly(4-aminostyrene); poly(diallyldimethylammonium chloride);polyhexamethylene guanidine; polyhexanide; poly(methylene co-guanidine);or poly(acrylamide-co-diallyldimethylammonium chloride).
 10. Thecomposition of any one of claims 1 to 9, wherein a hydrophobic groupcomprises a group selected from: a C2-C22 branched, linear, saturated orunsaturated, or cyclic alkyl; or an aryl.
 11. The composition of claim10, wherein the C2-C22 alkyl group is selected from the group consistingof: butyl; hexyl or octyl group.
 12. The composition of claim 10,wherein the C2-C22 alkyl group is selected from the group consisting of:isobutyl; isohexyl; or isooctyl group.
 13. The composition of claim 10.wherein the C2-C22 alkyl group is selected from a cycloalkyl selectedfrom the group consisting of: cyclohexyl; cycloheptyl; and cyclooctylgroup.
 14. The composition of claim 10, wherein the aryl group isselected from phenol; or phenyl group.
 15. The composition of any one ofclaims 1 to 9, wherein a hydrophobic group comprises a poly orperfluoroalkyl group, suitably a C8 perfluorooctane or C8polyfluorinated, 6:2 fluorotelomer.
 16. The composition of any one ofclaims 1 to 15, wherein the sorbent molecule comprises a plurality ofhydrophobic groups.
 17. The composition of any one of claims 1 to 15,wherein the polyamine group is linked to the hydrophobic group via abond selected from the group consisting of: an amide bond; a urealinkage; a thiourea linkage; an isothiouronium linkage; a guanidiniumlinkage and a quaternisation (Menshutkin) reaction.
 18. A process forremoval of a target substance from a fluid stream comprising contactingthe fluid stream with a composition comprising a polyamine; and acovalently linked hydrophobic group, wherein the polyamine is covalentlylinked to a support material.
 19. The process of claim 18, wherein thefluid is a liquid, optionally the liquid is selected from: water; anorganic solvent; a liquid fossil fuel; a liquid lubricant; an ionicliquid; and a working fluid.
 20. The process of claim 18, wherein thetarget substance comprises one or more poly- and perfluorinated alkylsubstance (PFAS), optionally selected from a perfluorinated anionicsurfactant compound, including one or more selected from the groupconsisting of: perfluorobutane sulfonate (PFBS); perfluorobutanoic acid(PFBA); perfluorohexanesulfonate (PFHS); perfluorohexanoic acid (PFHA);perfluorooctanoic acid (PFOA); perfluorooctane sulfonate (PFOS);perfluorononanoic acid (PFNA); and perfluorodecanoic acid (PFDA); and6:2 fluorotelomer sulfonic acid (6:2 FTSA).
 21. The process of claim 18,wherein the target substance comprises a valuable substance. optionallycomprising precious metals, rare earth metals, or platinum group metals,or salts thereof.
 22. The process of any one of claims 18 to 21, whereinthe support material comprises one or more of the group consisting of: alignocellulose; a bacterial cellulose; a microfibrillated cellulose; amicrocrystalline cellulose; and a cellulose derivative.
 23. The processof claim 22, wherein the support material is a cellulose orlignocellulose powder or pulp.
 24. The process of claim 22, wherein thecellulose or lignocellulose powder or pulp is incorporated into amembrane or membrane-like filter.
 25. The process of any one of claims18 to 21, wherein the support material is selected from one or more ofthe group consisting of: silica; silica gel; and a silica derivative.26. The process of any one of claim 18 to 22 or 25, wherein the supportmaterial is porous, solid, and particulate.
 27. The process of claim 26,wherein the porous, solid, particulate support material is in the formof one or more of the group consisting of: granules; flakes; beads;pellets; and pastilles.
 28. The process of any one of claims 18 to 27,wherein the support material is comprised within a bed or a packedcolumn and the fluid stream is passed through or across the bed orpacked-column.
 29. The process of any one of claims 18 to 28, whereinthe polyamine is selected from a linear or branched polyamine.
 30. Theprocess of claim 29, wherein the linear or branched polyamine isselected from the group consisting of: polyethylenimine (PEI);polypropylenimine (PPI); poly(allylamine); poly(vinylamine);poly(N-methylvinylamine); polylysine; poly(4-aminostyrene);poly(diallyldimethylammonium chloride); polyhexamethylene guanidine;polyhexanide; poly(methylene co-guanidine); orpoly(acrylamide-co-diallyldimethylammonium chloride).
 31. The process ofany one of claims 18 to 30, wherein a hydrophobic group comprises agroup selected from: a C2-C22 branched, linear or cyclic alkyl; or anaryl.
 32. The process of claim 31, wherein the C2-C22 alkyl group isselected from a butyl hexyl or octyl group.
 33. The process of claim 31,wherein the C2-C22 alkyl group is selected from an isobutyl isohexyl orisooctyl group.
 34. The process of claim 31, wherein the C2-C22 alkylgroup is selected from a cycloalkyl selected from a cyclohexyl,cycloheptyl or cyclooctyl group
 35. The process of claim 31, wherein thearyl group is selected from a phenol; or phenyl group.
 36. The processof any one of claims 18 to 30, wherein a hydrophobic group comprises apoly or perfluoroalkyl group, suitably a C8 perfluorooctane or C8polyfluorinated, 6:2 fluorotelomer
 37. The process of any one of claims18 to 36, wherein the sorbent molecule comprises a plurality ofhydrophobic groups.
 38. The process of any one of claims 18 to 37,wherein the polyamine group is linked to the hydrophobic group via anamide bond, a urea linkage, a thiourea linkage an isothiouroniumlinkage, a guanidinium linkage or a quaternisation (Menshutkin)reaction.
 39. The process of any one of claims 18 to 38, wherein theprocess further comprises regenerating the composition after removal ofthe contaminant substance from the fluid stream.
 40. The process ofclaim 39, wherein regenerating the composition comprises applying one ormore aqueous liquid washes to the composition.
 41. The process of claim40, wherein one or more of the liquid washes is a salt wash, optionallywherein the salt is selected from one or more of the group consisting ofa sodium, potassium or magnesium salt with a chloride, sulphate orphosphate counter ion.
 42. The process of claim 40 or 41, wherein one ormore of the liquid washes is an acid wash, optionally wherein the acidis selected from one or more of the group consisting of hydrochloricacid, sulphuric acid, nitric acid, phosphoric acid, ethanedioic acid,hexanoic acid, ethanedioic acid or citric acid.
 43. The process of anyone of claims 40 to 42, wherein one or more of the liquid washes is abasic wash, optionally wherein the base is selected from one or more ofthe group consisting of ammonium hydroxide, sodium hydroxide andpotassium hydroxide.
 44. The process of claim 43, wherein the basic washcomprises ammonium hydroxide.
 45. The process of any of claims 40 to 44,wherein one or more of the liquid washes has a pH has a pH greater than9.
 46. The process of any of claims 40 to 44, wherein one or more of theliquid washes has a pH has a pH less than
 5. 47. A method formanufacturing a composition for removal of a contaminant substance froma fluid stream, the method comprising: a. providing a support material;and b. linking the support material covalently to a contaminant-sorbentmolecule comprising a polyamine group; and a covalently linkedhydrophobic group.